高压挤注条件下疏松砂岩储层破坏模式及模拟研究

发布时间：2018-08-23 19:02

【摘要】：疏松砂岩油气藏管外充填防砂技术主要包括塑性挤压充填和压裂充填两种模式,两种充填模式的选择取决于对施工条件、地质情况的综合判断。但长期以来对于高压挤注充填条件下疏松砂岩地层的破坏机理认识不透彻,对破坏模式没有建立系统的识别方法,理论研究与实际应用脱节,导致工艺技术和施工参数不甚合理,影响了高压管外充填一体化防砂技术的进一步发展。本文综合考虑高压挤注条件下疏松砂岩地层的复杂变形过程,建立了高压挤注条件下疏松砂岩地层应力分布规律的多孔介质模型,并将其推广到任意井身结构的定向井或水平井。考虑高压挤注充填条件下携砂液瞬态温度效应,探讨热应力对挤注条件下疏松砂岩岩石破坏模式的影响。结果表明,携砂液的瞬态温度效应对地层破坏临界值及地层破坏形态的影响较小,工程计算中可以忽略不计。本文在继承前人研究成果的基础上,将疏松砂岩地层岩石划分为脆性岩石、韧性岩石和可压缩性岩石三种类型,分别分析了三种岩石宏观破坏差异性在岩石力学特性方面的表现。从岩石本身特性和人为因素两个方面阐述了高压挤注条件下疏松砂岩地层破坏形态的影响因素。通过分析认为脆性岩石一般服从拉伸破坏准则,韧性岩石受剪切破坏准则的控制,而可压缩性岩石则受到压实破坏机理的控制。基于弹-理想塑性本构模型分析高压挤注条件下韧性岩石的破坏模式,建立了韧性地层破坏后地层形态的判别方法、韧性岩石的破坏临界值计算方法、人工裂缝启裂临界压力计算方法和裂缝延伸压力计算方法。通过模拟计算和矿场实际数据分析表明:Mohr-Coulomb模型能较好的反映地层的剪切破坏过程,韧性地层高压挤注条件下形成有效人工裂缝的前提是井壁处径向应力为中间应力,否则,地层周围将产生较为均质的剪切破碎带,无法形成压裂剪切裂缝。在分析高压挤注过程中可压缩性岩石微观变形规律的基础上,应用修正剑桥模型建立了高压挤注条件下可压缩性岩石的井底塑性破坏临界压力值计算模型,以及一定压力条件下的井底塑性压实破坏半径预测方法。通过模拟研究表明:地层应力非均质性是导致疏松砂岩可压缩性岩石压实破坏非均质性的根本原因,压实破坏临界井底压力及塑性压实破坏半径随着井周角的变化呈现周期性的变化规律,在最大主应力方向上的岩石首先发生压实破坏,井底压力越大,塑性压实破坏半径越大。论文的研究成果对于进行地层压裂充填可行性分析以及高压挤注充填参数的设计具有重要的借鉴意义,对于未来形成一体化挤注充填现场施工技术提供了基础和条件。
[Abstract]:The sand control technology of loose sandstone reservoir is mainly composed of plastic extrusion filling and fracturing filling. The selection of the two filling modes depends on the comprehensive judgment of the construction conditions and geological conditions. However, for a long time, the failure mechanism of loose sandstone formation under the condition of high pressure extrusion and filling has not been fully understood, there is no systematic identification method for the failure mode, and the theoretical research is out of touch with the practical application. As a result, the technology and construction parameters are not reasonable, which affects the further development of the integrated sand control technology. In this paper, considering the complex deformation process of loose sandstone formation under high pressure extrusion, a porous medium model for stress distribution of loose sandstone formation under high pressure extrusion condition is established. It is extended to directional wells or horizontal wells with arbitrary shaft structure. Considering the transient temperature effect of sand carrying fluid under the condition of high pressure extrusion and filling, the effect of thermal stress on the failure mode of loose sandstone rock under extrusion condition is discussed. The results show that the transient temperature effect of sand carrying fluid has little effect on the critical value of formation failure and formation failure form, which can be ignored in engineering calculation. In this paper, the loose sandstone strata are divided into three types: brittle rock, ductile rock and compressible rock. The performance of three kinds of rock macroscopic failure difference in rock mechanics characteristic is analyzed respectively. In this paper, the influence factors of loose sandstone formation failure form under the condition of high pressure extrusion are expounded from the characteristics of rock itself and human factors. It is considered that brittle rock is generally subjected to tensile failure criterion, ductile rock is controlled by shear failure criterion, and compressible rock is controlled by compaction failure mechanism. Based on the elastic-ideal plastic constitutive model, the failure model of ductile rock under high pressure extrusion is analyzed, and a method to distinguish the formation morphology and calculate the critical value of failure of ductile rock is established. The method of calculating the critical pressure of artificial crack initiation and the method of calculating fracture extension pressure. Through simulation calculation and field data analysis, it is shown that the 1: Mohr-Coulomb model can better reflect the shear failure process of the formation. The premise of forming effective artificial fractures under the condition of high pressure extrusion in the ductile formation is that the radial stress at the wellbore is intermediate stress, otherwise, There will be homogeneous shear fracture zone around the formation, which can't form fracturing and shear fracture. On the basis of analyzing the microscopic deformation law of compressible rock during high pressure extrusion, a model for calculating the critical pressure of bottom hole plastic failure of compressible rock under high pressure extrusion is established by applying the modified Cambridge model. And the prediction method of bottom hole plastic compaction failure radius under certain pressure condition. The simulation results show that the heterogeneity of formation stress is the fundamental cause of compaction and destruction of unconsolidated sandstone compressible rock. The critical bottom pressure of compaction failure and the radius of plastic compaction failure change periodically with the change of well circumference angle. The rock in the direction of maximum principal stress first occurs compaction failure, and the larger the bottom hole pressure, the larger the radius of plastic compaction failure. The research results of this paper have important reference significance for the feasibility analysis of formation fracturing and filling and the design of high pressure injection filling parameters, and provide the foundation and condition for the formation of integrated injection and filling field construction technology in the future.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE358.1

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